1. Field of the Invention
This invention pertains to the production of layered structures such as compound panes.
2. Related Art
Compound panes used in construction and in transportation vehicles, especially as windshields, are generally formed of at least one rigid sheet such as a sheet of glass or plastic material like polycarbonate or polymethacrylate of methyl, and of at least one sheet of a more flexible plastic material, such as polyvinylbutyral or polyurethane, for example, generally utilized as an intermediate sheet in the case of a structure comprising two rigid sheets.
To produce these compound panes, one cuts the sheets of flexible plastic material beforehand to the exact size and shape of the pane or to a slightly larger geometric format to form a primitive. The primitives are stacked with the other constituent elements of the compound pane and all of these elements are put together during an assembly operation which is generally performed in two stages: a first stage consisting, for example, of a calendering process providing a preliminary assembly, followed by a second stage consisting of a pressure sealing stage, in which high temperature and pressure are used to form the final assembly
The invention pertains more specifically to the stacking of the flexible sheet with the other constituent elements of the compound pane and the operations related thereto, especially the gripping of the flexible plastic sheet at a storage station near the stacking station, the transferral thereof to the stacking station and the placement thereof in the correct position in the stacked formation.
One of the problems which is encountered in the automation of the various operations utilized for the production of compound panes is the gripping of the sheet made of plastic material at the storage station and its correct positioning in the stacked formation forming the pane. Indeed, sheets made of plastic material such as polyvinylbutyral or polyurethane tend to stick together to a certain degree when exposed to the surrounding temperatures present in a factory and when they are stacked together which is generally the case at the storage station. For the gripping of the sheet, it commonly occurs that when the top sheet on the pile is gripped, the sheet subjacent thereto is also taken, essentially adhering to the former. This phenomenon is particularly troublesome when the sheets are placed at a fixed and specific location, which is the case in an automated assembly process in which the sheet is intended to be gripped in a specific place and transferred over a path having a constant length to the station where the compound pane is stacked. As a result, if the pane were moved from its exact gripping position, it would subsequently be placed in an accordingly offset and thus incorrect position in the stacked formation.